<![CDATA[This research was aimed to describe the practicality, effectiveness, and effect size of discovery learning model to improve the ability of the students original thinking of solution electrolyte and non electrolyte topics. The research sample was X.2 class at SMAN 6 Metro which it was obtained by using cluster random sampling. This research used poor experimental method with one group pretest-posttest design. Practicality was measured by implementation of discovery learning model and students response. Effectiveness was measured by basis of teacher ability, students activity, and the ability of the students original thinking used difference of two average test and effect size test. The result of this research shown that the practicality and effectivity of discovery learning model had high criteria, n-gain average was 0.70 and effect size was 0.98.Based on them, discovery learning model was practical, effective, and big effect size to improve the ability of the students original thinking of solution electrolyte and non electrolyte topics.Penelitian ini bertujuan mendeskripsikan kepraktisan, keefektivan, dan ukuran pengaruh modeldiscovery learningdalam meningkatkan kemampuan berpikir orisinil siswa pada materi larutan elektrolit dan non elektrolit. Sampel yang digunakan dalam penelitian ini adalah kelas X.2 di SMAN 6 Metro yang diperoleh dengan menggunakancluster random sampling. Penelitian ini menggunakan metodepoor experimentaldenganone group pretest-posttest design. Kepraktisan ditentukan berdasarkan keterlaksanaan modeldiscovery learningdan respon siswa. Keefektivan ditentukan berdasarkan kemampuan guru, aktivitas siswa, dan kemampuan berpikir orisinil siswa menggunakan uji perbedaan dua rata-rata dan uji ukuran pengaruh. Hasil penelitian menunjukkan bahwa kepraktisan dan keefektivan modeldiscovery learningberkriteria tinggi, nilai rata-ratan-gain sebesar 0,70 dan ukuran pengaruh sebesar 0,98. Berdasarkan hal tersebut, modeldiscovery learningpraktis, efektif dan memiliki ukuran pengaruh yang besar dalam meningkatkan kemampuan berpikir original siswa pada materi larutan elektrolit dan non elektrolit.Kata kunci:discovery learning, elektrolit dan non elektrolit, kemampuan berpikir orisinil]]>
